1. Field of the Invention
The present invention relates to a novel phosphorus-containing phenolic resin and a method for manufacturing the same. More specifically, the present invention relates to a phenolic resin composition including a novel phosphorus-containing phenolic resin, an epoxy resin curing agent including the phenolic resin composition, an epoxy resin composition including the epoxy resin curing agent and an epoxy resin, a cured product obtained by curing the epoxy resin composition, and a copper-clad laminated plate obtained by using the epoxy resin composition as a matrix resin.
2. Background
Phenolic resins are suitable for use as curing agents for epoxy resins. An epoxy resin composition using a phenolic resin as a curing agent has various advantages such as high heat tolerance and moisture resistance, such that the composition is widely used in the field of semiconductors or electronic elements as a material for a printed wiring board, an interlayer insulating material for a buildup substrate, a semiconductor encapsulating material, a material for a conductive binder, etc.
In recent years, in a step for mounting a printed wiring board, the conventionally used lead solder has been switched to lead-free solder after taking account of environmental protection. The melting temperature of the lead-free solder is higher than that of the lead solder by about 20 to 40° C. Therefore, the temperature used in the mounting step must be increased. Moreover, the heat tolerance of the material for the printed wiring board, or the encapsulating material needs to be further increased. Especially, the moisture resistance of these materials is required to be improved when the goal is to prevent cracks from forming during moisture absorption and reflow soldering. Furthermore, as the amount of information transmitted is augmented and communication becomes high speed, signals need to be made into short wavelengths (i.e., high frequency) in order to be transmitted at a large quantity per unit of time. To achieve the above, low permittivity and a low dissipation factor are required.
Furthermore, flame retardation is typically required for electronic elements such as printed wiring boards. When an epoxy resin composition is being used as a material for a printed wiring board, a halogen-based flame retardant, such as a bromine-based flame retardant, is often combined and blended with an antimony compound to impart flame retardation. However, for the environmental/safety strategies in recent years, there is a strong demand to develop a flame retardation method which does not use a combination of a halogen-based flame retardant and an antimony compound and conform to the environmental/safety strategy.
To meet the demand, flame retardation by using phosphorus-containing compounds has been discussed. For example, the methods of adding phosphorus-based flame retardants, such as phosphate-based compounds like triphenyl phosphate (TPP), tricresyl phosphate (TCP) or cresyl diphenyl phosphate (CDP) in epoxy resin compositions have been discussed.
For example, patent document 1 (JP 2001-220427) proposes a flame-retardant epoxy resin curing agent containing an active hydrogen atom, which introduces a group containing a phosphorus atom into a specific phenolic compound.
Although the flame retardant epoxy resin curing agent having an active hydrogen atom, as proposed in patent document 1, can improve flame retardation and inhibit the generation of harmful substances during burning, it cannot satisfy the requirements of various properties such as moisture resistance, permittivity and the dissipation factor.